Most air travelers have experienced turbulence at some point during flight. In addition to being uncomfortable for passengers, turbulence poses a threat of damage to aircraft, as well as a threat of injury to passengers and crew. Indeed, the United States Federal Aviation Administration (FAA) presently requires that aircraft experiencing severe turbulence undergo inspection prior to returning to service, and at least one source has estimated that turbulence costs US airlines over $100 million per year in expense and lost revenue. Avoiding turbulence, then, has economic benefits in addition to the obvious benefits in terms of comfort and safety.
At present, turbulent air lying in the path of an aircraft is relatively difficult to identify. Various turbulence detection systems based upon Doppler radar or lidar have met with some success, but these systems are generally based upon radio frequency reflections off of particulate matter in the air, so their use is limited at many cruising altitudes that are above cloud layers and that are relatively free of dust or other particulates. Other systems that rely upon pilot reports (PIREPS) or automatic reporting from accelerometers on board existing aircraft can be beneficial as well, but these techniques are inherently unable to predict turbulence in areas where an aircraft has not previously experienced turbulent air. More recently, some attempts have been made to predict turbulent air using variations in global positioning system (GPS) signals. These systems, while effective in many settings, are presently quite expensive, and they are not typically intended to detect close range turbulence (such as wake turbulence generated by other aircraft). As a result, there remains a need and a desire for a turbulence detection system that is capable of effectively identifying various types of turbulence (including close range turbulence and clear air turbulence) without requiring an aircraft to venture into the turbulent airspace.